The present invention relates to a stator of a rotary electric machine with a plurality of poles, the stator including a stator core and polyphase coils, the stator core having teeth that define therebetween a plurality of slots, the polyphase coils being provided in the slots, each phase of the polyphase coils having a plurality of coils that are formed for each pole and connected in parallel.
In some rotary electric machines, the rotor and the stator are disposed eccentrically with respect to each other. In the stator wherein coils are connected in parallel, imbalance of electromotive force caused by the eccentricity may generate cyclic current in the parallel circuit thereby to cause an increase of noise and of vibration of the rotary electric machine during the operation. In order to reduce the cyclic current, Japanese Unexamined Patent Application Publication No. 2006-311716 discloses a winding structure of a rotary electric machine.
The stator winding of this Publication includes a U-phase coil, a V-phase coil and a W-phase coil. Referring to FIG. 10, one end of the U-phase coil 1100 is connected to a U-phase terminal 120U of a three-phase cable and the other end serves as a neutral point N. The U-phase coil 110U includes U-phase coils 111U-118U. The U-phase coils 111U, 112U, 115U, 116U are connected in series to form a first coil group A. The U-phase coils 113U, 114U, 117U, 118U are connected in series to form a second coil group B. The first coil group A and the second coil group B are connected in parallel.
The first coil group A is so arranged that the U-phase coils 111U, 112U and 115U, 116U are spaced from each other in the circumferential direction of the stator core 100 and face each other in the radial direction of the stator core 100. The second coil group B is so arranged that the U-phase coils 113U, 114U and 117U, 118U are spaced from each other in the circumferential direction of the stator core 100 and face each other in the radial direction of the stator core 100. Therefore, in a rotary electric machine having the rotor and the stator disposed eccentrically with respect to each other, the electromagnetic balance is kept thereby to reduce the cyclic current flowing between the first coil group A and the second coil group B connected in parallel.
A part of the wire connecting the U-phase coils 112U and 115U of the first coil group A to each other is wound around the same teeth around which the U-phase coil 113U of the second coil group B is also wound, as indicated by the dashed line in FIG. 10. A part of the wire connecting the U-phase coils 114U and 117U of the second coil group B to each other is wound around the same teeth around which the U-phase coil 116U of the first coil group A is also wound, as indicated by the dashed line in FIG. 10. In the structure wherein the connecting wires are used as a part of the coils and provided in the slots, the coil end of the stator is downsized.
Since the U-phase coils of each of the first coil group A and the second coil group B are spaced from each other to face each other, the connecting wires of the spaced U-phase coils are increased in length thereby to deteriorate the productivity in manufacturing of the coils.
The present invention is directed to providing a stator of a rotary electric machine with a plurality of poles, which prevents generation of the cyclic current flowing between the coils connected in parallel and also improves the productivity in manufacturing of the coils.